The present disclosure relates to a direct type backlight.
At present, in the Flat Panel Display (FPD) technology, as liquid crystal displays (LCDs) have such advantages as being light, thin, short and small, as well as greatly saving the space for placing them, they have been gradually replacing cathode ray tube (CRT) displays to become the mainstream of displays. Because a LCD panel does not emit light itself, it is necessary to provide a light emitting source on the LCD panel so that the LCD can display image. Thus, a backlight is indispensable for a LCD.
In the related art, according to positions of backlights in LCDs, the backlights can be categorized into two types, i.e. side-light type backlights and direct type backlights, wherein a side-light type backlight is positioned at a side of a display screen of a LCD, whereas a direct type backlight is positioned direct under a display screen of a LCD. As for a side-light type backlight, light from a bar-like light emitting source are converted into surface light source mainly by a light guide plate.
As shown in FIG. 1, which is a schematic view of a cross-section structure of a direct type backlight in the related art, the direct type backlight comprises several light emitting bodies 11 arranged in parallel, a reflecting sheet 12, a back plate 13, and a diffusing plate 14, wherein the back plate 13 has a supporting function, a distance between the light emitting bodies 11 and the diffusing plate 14 is called a light mixing distance, and after passing through the light mixing distance, the light emitted from the light emitting bodies 11 reaches the diffusing plate 14, which diffuses the light to form a surface light source that can be output.
When the light emitting bodies 11 are light emitting diodes (LEDs), the brightness in the center of the light emitting body 11 is relatively high, whereas the brightness at edges is relatively low. Thus, if the distance between the light emitting bodies 11 and the diffusing plate 14 is too close, there might be multiple bright lines or bright spots when the LCD panel is illuminated with the direct type backlight, causing a non-uniform light distribution on the LCD panel, and affecting image quality of the LCD panel severely. FIG. 2 shows a schematic view of the brightness distribution of the light projected onto the LCD panel for the direct type backlight in the related art. In FIG. 2, the horizontal axis represents the abscissa value of the light projected onto the LCD panel, and the vertical axis represents the brightness value of the light. As can be seen in FIG. 2, the distribution of the light projected onto the LCD panel by the direct type backlight is not uniform.
In view of the above problem, it is proposed in the related art to increase the light mixing distance between the light emitting bodies 11 and the diffusing plate 14 to ensure a uniform distribution of the light on the LCD panel. However, this approach makes the thickness of the direct type backlight too thick, and thus makes the thickness of the entire LCD too thick, which is totally against the current need for a light-weighted and thin liquid-crystal display.